Natural conception: repeated predictions over time.
How can we predict chances of natural conception at various time points in couples diagnosed with unexplained subfertility?
We developed a dynamic prediction model that can make repeated predictions over time for couples with unexplained subfertility that underwent a fertility workup at a fertility clinic.
The most frequently used prediction model for natural conception (the 'Hunault model') estimates the probability of natural conception only once per couple, that is, after completion of the fertility workup. This model cannot be used for a second or third time for couples who wish to know their renewed chances after a certain period of expectant management.
A prospective cohort studying the long-term follow-up of subfertile couples included in 38 centres in the Netherlands between January 2002 and February 2004. Couples with bilateral tubal occlusion, anovulation or a total motile sperm count <1 × 106 were excluded.
The primary endpoint was time to natural conception, leading to an ongoing pregnancy. Follow-up time was censored at the start of treatment or at the last date of contact. In developing the new dynamic prediction model, we used the same predictors as the Hunault model, i.e. female age, duration of subfertility, female subfertility being primary or secondary, sperm motility and referral status. The performance of the model was evaluated in terms of calibration and discrimination. Additionally, we assessed the utility of the model in terms of the variability of the calculated predictions.
Of the 4999 couples in the cohort, 1053 (21%) women reached a natural conception leading to an ongoing pregnancy within a mean follow-up of 8 months (5th and 95th percentile: 1-21). Our newly developed dynamic prediction model estimated the median probability of conceiving in the first year after the completion of the fertility workup at 27%. For couples not yet pregnant after half a year, after one year and after one and a half years of expectant management, the median probability of conceiving over the next year was estimated at 20, 15 and 13%, respectively. The model performed fair in an internal validation. The prediction ranges were sufficiently broad to aid in counselling couples for at least two years after their fertility workup.
The dynamic prediction model needs to be validated in an external population.
This dynamic prediction model allows reassessment of natural conception chances after various periods of unsuccessful expectant management. This gives valuable information to counsel couples with unexplained subfertility that are seen for a fertility workup.
This study was facilitated by grant 945/12/002 from ZonMW, The Netherlands Organization for Health Research and Development, The Hague, The Netherlands. No competing interests.
van Eekelen R
，Scholten I
，Tjon-Kon-Fat RI
，van der Steeg JW
，Steures P
，Hompes P
，van Wely M
，van der Veen F
，Mol BW
，Eijkemans MJ
，Te Velde ER
，van Geloven N
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Semen parameter thresholds and time-to-conception in subfertile couples: how high is high enough?
What thresholds for total sperm count, sperm concentration, progressive motility, and total progressive motile sperm count (TPMC) are associated with earlier time-to-conception in couples undergoing fertility evaluation?
Values well above the World Health Organization (WHO) references for total sperm count, concentration, and progressive motility, and values up to 100 million for TPMC were consistently associated with earlier time-to-conception and higher conception rates.
Although individual semen parameters are generally not able to distinguish between fertile and infertile men, they can provide clinically useful information on time-to-pregnancy for counseling patients seeking fertility treatment. Compared to the conventional semen parameters, TPMC might be a better index for evaluating the severity of male infertility.
We used data from a longitudinal cohort study on subfertile men from 2002 to 2017 and included 6061 men with initial semen analysis (SA) in the study.
Men from subfertile couples who underwent a SA within the study period were included, and 5-year follow-up data were collected to capture conception data. Couples were further categorized into two subgroups: natural conception (n = 5126), after separating those who achieved conception using ART or IUI; natural conception without major female factor (n = 3753), after separating those with severe female factor infertility diagnoses. TPMC was calculated by multiplying the semen volume (ml) by sperm concentration (million/ml) and the percentage of progressively motile sperm (%). Cox proportional hazard models were used to report hazard ratios (HRs) with 95% CIs before and after adjusting for male age, the number of previous children before the first SA, and income. Using the regression tree method, we calculated thresholds for total sperm count, sperm concentration, progressive motility, and TPMC to best differentiate those who were more likely to conceive within 5 years after first SA from those less likely to conceive. We also plotted continuous values of semen parameters in predicting 5-year conception rates and time-to-conception.
Overall, the median time to conception was 22 months (95% CI: 21-23). A total of 3957 (65%) couples were known to have achieved conception within 5 years of the first SA. These patients were younger and had higher values of sperm concentration, progressive motility, and TPMC. In the overall cohort, a TPMC of 50 million best differentiated men who were more likely to father a child within 5 years. Partners of men with TPMC ≥50 million had a 45% greater chance of conception within 5 years in the adjusted model (HR: 1.45; 95% CI: 1.34-1.58) and achieved pregnancy earlier compared to those men with TPMC < 50 million (median 19 months (95% CI: 18-20) versus 36 months (95% CI: 32-41)). Similar results were observed in the natural conception cohort. For the natural conception cohort without major female factor, the TPMC cut-off was 20 million. In the visual assessment of the graphs for the continuous semen parameter values, 5-year conception rates and time-to-conception consistently plateaued at higher values of sperm concentration, total sperm count, progressive motility, and TPMC compared to the WHO reference levels and our calculated thresholds. For TPMC, values up to 100-150 million were still associated with a better conception rate and time-to-conception in the visual assessment of the curves.
There was limited information on female partners and potential for inaccuracies in capturing less severe female infertility diagnoses. Also we lacked details on assisted pregnancies achieved outside of our healthcare network (with possible miscoding as 'natural conception' in our cohort). We only used the initial SA and sperm morphology, another potentially important parameter, was not included in the analyses. We had no information on continuity of pregnancy attempts/intention, which could affect the time-to-conception data. Finally, most couples had been attempting conception for >12 months prior to initiating fertility treatment, so it is likely that we are underestimating time to conception. Importantly, our data might lack the generalizability to other populations.
Our results suggest that a TPMC threshold of 50 million sperm provided the best predictive power to estimate earlier time-to-conception in couples evaluated for male factor infertility. Higher values of sperm count, concentration and progressive motility beyond the WHO references were still associated with better conception rates and time-to-conception. This provides an opportunity to optimize semen parameters in those with semen values that are low but not abnormal according to the WHO reference values. These data can be used to better inform patients regarding their chances of conception per year when SA results are used for patient counseling.
None.
N/A.
Keihani S
，Verrilli LE
，Zhang C
，Presson AP
，Hanson HA
，Pastuszak AW
，Johnstone EB
，Hotaling JM
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ResearchGate
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